As is well known, in the field of high-pressure fluid treatment, in particular with regard to emulsion micronization applications, stabilization of dispersions and controlled cellular rupture/breakup of a fluid, devices called homogenizers are frequently used. Such devices generally comprise a pump with pistons that move with alternating motion by means of a crankshaft (or camshaft), are synchronous and mutually offset by an angle of 360°/n where n is the number of pumping pistons that move and raise the pressure of the fluid inside the processing part of the machine (the number of pistons generally ranges from one to a maximum of eight pistons).
In particular, homogenizers comprise an adjustable valve (called homogenizing valve), which effects a forced passage of the fluid to be treated from a high pressure area to a low pressure area, or in any case one of lower pressure. The piston pump is located upstream of the valve and is driven by an electric motor which moves the crankshaft.
Interposed between the motor and the pump there is also a reduction gear unit consisting of a pulley system and, where present, a parallel axis or epicyclic reduction gear system.
This kinematic chain serves to convert the rotary motion of the shaft into alternating rectilinear motion, transmitting it rigidly to the pump pistons.
Each piston thus generates a pulsating compression action on the fluid to be treated. The individual piston pulsations are combined together (in relation to the fixed offset introduced by the relative angles between the various cranks of the crankshaft) in a manifold, generating a single resulting pulsation which is directly felt by the homogenizing valve.
Each pumping piston generates, in its own compression chamber, a pulsating pressure ranging from 0 to pmax bar, where pmax=max value the machine is configured for, which may be even greater than 2000 bar.
If the homogenizer is equipped with only one piston, the entire pulsation 0−pmax is also felt in the same way by the homogenizing valve and by the elements (e.g. transducer) downstream of the pumping valves.
In the case of a plurality of pistons, the amplitude of the resulting pulsations is dampened compared to the case of pumps consisting of a single piston, but is nonetheless perceived downstream of the pump.
Moreover, the crankshaft (or camshaft) is constructed with relative fixed angles between cranks and thus the offset between the pulsations also remains fixed. Consequently, the resulting pulsation, though dampened, is never eliminated but rather always remains constant.
However, the known homogenizers described above exhibit a series of disadvantages, mostly tied to the life cycle of the individual components.
In fact, the pressure and pulsating flow of the fluid results in considerable potential impacts against the moving mechanical parts of the homogenizing valve.
These impacts, affecting the respective mobile element of the valve which works at short axial distances relative to the fixed element, tend to damage the entire structure of the valve, especially in the low peak phases of the pulsations.
Moreover, the pumping action subjects the individual components subjected to pulsations to a fatigue load cycle which results in a considerable reduction in the life cycle of such components.
The wear on the components (which determines the life cycle thereof) is directly proportional to the rpm of the crankshaft (pulsation frequency) and the fluid pumping pressures.
For this reason, at high operating performances (pumping speed and pressure) all of the components cooperating in the compression will have a very short life cycle.
U.S. Pat. No. 6,827,479 discloses a nozzle valve with a fixed geometry and a system for controlling forward travel speeds of the oil hydraulic pistons, wherein the control of the piston travel speeds directly regulates the pressure (without having freedom of action over the latter). In practical terms, once the forward travel speed of the pistons is fixed (law of motion and hence flow rate), the homogenization pressure is automatically fixed and the system substantially has only one degree of freedom.